In the context of manufacturing fibre-reinforced parts, such as blades, for wind power plants, a manufacturing process is typically employed in which a part is moulded in two halves in each their open mould, wherein a coat e.g. of gelcoat is initially applied onto the interior surface of the open mould.
A number of layers of fibre material, or mats, are subsequently arranged in the mould, typically by hand, following which resin is applied, typically by injection into the closed mould, to attach the individual layers of fibre material to each other. The resin can be applied to the layers manually by RTM (resin transfer moulding), VARTM (vacuum assisted resin transfer moulding) or other suitable methods. Alternatively the resin can be applied to the laminate layers prior to laying the layers (Prepeg). In the context of this, gelcoat will harden and form the surface of the product.
The layers are typically provided to the process as rolls comprising an “endless” length of material which are arranged on the mould and subsequently cut to fit the shape of the part to be manufactured.
Arranging and shaping (by cutting) the layers of fibre material within the interior of a mould is today a time-consuming and labour intensive process. Depending of the size of the part to be manufactured, and thereby the size of the mould, walkways may be arranged alongside and/or above the mould such that the workers are allowed to walk along the edge or periphery of the mould and/or above the mould in order to arrange and cut the layers of fibre material as required.
During the layup of fibre material, combined efforts of several workers are required, as the fibre material is heavy and not easy manipulable. Some workers assist in the rollout of material, while other workers positioned along the edge of the mould, make sure that the layers are laid up correctly.
In order to secure a desired shape, visual appearance, strength and stability of the part to be manufactured, it is of outmost importance that the layers are arranged and cut correctly without dents or wrinkles and the like.
Depending on the application and structure of the part to be manufactured, multiple layers of fibre material may be arranged on the mould and the layers are typically arranged on top of each other or next to each other possibly with overlapping edges.
The parts typically consist of as many as fifty or more layers of material, and the parts are typically build up from a main laminate provided in the centre of the mould.
After a layer, which is provided from a roll, is arranged on the mould, the material is cut from the roll. Manufacturing of parts having curvature throughout the length of the part, such as a wing for a wind power plant, may require very long cuts along the edges of the mould.
Moulds for manufacturing such parts may be very large, and the moulds are as a consequence expensive. The time required for the arrangement of material on the mould should be kept at a minimum such that the form time (the time which a part occupies the mould) required by a part to be manufactured is kept at a minimum, thus increasing the overall productivity of the mould.
GB 2156729 A teaches a method of moulding reinforced materials where a pre-impregnated reinforcement material, such as a glass fibre mat, is applied to a moulding process. The reinforcement material may be of “indefinite length”, in which case a cutter will be needed for the process of laying up the laminate, or the mat can be provided to the process in pre-cut lengths, where the cuts are provided by a cutting station arranged in the vicinity of the mould. The cutting station is able to cut the material, prior to the material being arranged onto the mould, in a direction substantially transverse to the materials direction of conveyance.
The fibre material is preferably arranged substantially even and flush, which is why any developed dents, wrinkles or curls and the like should be smoothed out. Further, as one layer is typically applied on top of a preceding layer, the lower layer incl. possible additional layers arranged below the lower layer, tend to move or slide within the mould causing the entire layup of fibre material to move away from an intended position within the mould. As a consequence, any manipulation or handling of the material arranged on the mould should be kept at a minimum, which is why a process of manufacture is desired wherein the step of cutting the mats, while the mats are arranged on the mould, is eliminated.
It is thus an object of the invention to provide a solution to the above drawbacks.
This is accomplished by the method of manufacturing a fibre-reinforced part as per the introductory part of this specification, wherein each mat is arranged on the curved surface of the mould as pre-shaped mats having a form substantially corresponding to an intended area of application such that any need for further modification of or cutting in the mat is substantially eliminated.
The method according to the present invention substantially reduces the required form time required by the manufacturing of a part, and further, the method is able to reduce the efforts required by workers in order to lay up the mats.
When, as stated in claim 2, the pre-shaped mats are rolled off or drawn from one or more rolls provided on a gangway or a cart adapted for conveyance along said elongated mould, the odds of damaging the layers during the layup is greatly reduced and the required manpower for the layup minimized.
When, as stated in claim 3, the one or more rolls are arranged as a “revolver drum” comprising a number of rolls each comprising different pre-shaped mats, handling of, and access to the mats accommodated by the rolls are greatly optimized.
According to one embodiment, the pre-shaped mats constitute pre-cut mats cut from one or more rolls of material.
When, as stated in claim 5, the pre-shaped mats are arranged on the mould according to a pattern of predetermined positions, layup speed as well as the quality of the final product is increased.
According to one embodiment, the predetermined positions constitute a pattern established on the mould by means of light.
According to one embodiment the pre-shaped mats are provided from a device adapted to pre-cut an “endless” length of material drawn of a roll.
According to one embodiment, the pre-cut mats are rolled onto one or more rolls and in one or more layers.
When, as stated in claim 10, the pre-shaped mats are provided with a form of identification, control and documentation of the layup is facilitated.